|Year : 2008 | Volume
| Issue : 3 | Page : 107-113
Early class III occlusal tendency in children and its selective management
A Kapur1, HS Chawla1, A Utreja2, A Goyal1
1 Pedodontics & Preventive Dentistry, Oral Health Sciences Centre, Postgraduate Institute of Medical Education & Research, Chandigarh, India
2 Unit of Orthodontics, Oral Health Sciences Centre, Postgraduate Institute of Medical Education & Research, Chandigarh, India
Department of Oral Health Sciences Centre, PGIMER, Chandigarh
| Abstract|| |
Class III malocclusion may develop in children as a result of an inherent growth abnormality, i.e., true class III malocclusion, or as a result of premature occlusal contacts causing forward functional shift of the mandible, which is known as pseudo class III malocclusion. These cases, if not treated at the initial stage of development, interfere with normal growth of the skeletal bases and may result in severe facial deformities. The treatment should be carried out as early as possible with the aim of permitting normal growth. This paper deals with the selection of an appropriate treatment approach from the various current options available for early intervention in children developing class III occlusal tendencies; the different clinical features are depicted in the three case reports.
Keywords: Class III, face mask, twin block
|How to cite this article:|
Kapur A, Chawla H S, Utreja A, Goyal A. Early class III occlusal tendency in children and its selective management. J Indian Soc Pedod Prev Dent 2008;26:107-13
|How to cite this URL:|
Kapur A, Chawla H S, Utreja A, Goyal A. Early class III occlusal tendency in children and its selective management. J Indian Soc Pedod Prev Dent [serial online] 2008 [cited 2013 May 22];26:107-13. Available from: http://www.jisppd.com/text.asp?2008/26/3/107/43191
Developing class III malocclusion tendencies in children may have an underlying skeletal or dental component. Pseudo class III malocclusion is a habitual established crossbite of all anterior teeth, without any skeletal discrepancy, resulting from functional forward positioning/shift of the mandible on closure. It may begin with an unfavorable incisal guidance resulting from displaced eruption of a permanent incisor, with subsequent occlusal prematurities leading to anterior displacement of the mandible, disturbing the functional equilibrium. In children with pseudo class III malocclusion, when the mandible is 'guided' into a normal centric relation a normal overjet or an edge-to-edge position of incisors can be obtained. This is an important parameter in distinguishing it from true class III malocclusion. On cephalometric analysis, pseudo class III malocclusion shows a normal SNA if diagnosed early, whereas SNB could be slightly increased because of forward positioning of the mandible. In contrast, in true class III cases, a large SNB angle or a small SNA angle may be found, depending on whether the result is due to an underdeveloped maxilla or a long mandibular base, or both. In addition, the mandibular incisors may depict a retroclination, thus lessening the IMPA. In contrast, pseudo class III cases may show a retroclination of maxillary incisors and normal lower incisors.  Most true class III cases have a strong hereditary component and are a result of inherent saggital discrepancy, the environmental factors being of little importance in their genesis. The final diagnosis of the type of class III malocclusion relies heavily on (i) clinically establishing the dual closure pattern by asking and guiding the patient to bite in normal centric and habitual positions, (ii) observing any familial tendency, (iii) cephalometric parameters, and (iv) incisor relationships. Both these types of malocclusion, if untreated early, may affect the normal growth and development of the skeletal bases, leading to restricted maxillary growth and maybe mandibular overgrowth. Most of the cases are however a combination of the above factors, where there is (a) skeletal discrepancy which has been aggravated by a positional molar relation of the mandible or vice versa and (b) a prolonged positional malrelation causing a skeletal change. Both these conditions require intervention. In this paper we discuss the various factors affecting the choice of a suitable treatment modality and describe three cases of developing class III malocclusion treated using different approaches as per the presenting features.
| Case Reports|| |
An 8-year-old girl reported with the chief complaint of irregular placement of upper and lower front teeth. On extraoral examination a concave profile was noticed, with an appearance of maxillary growth restriction [Figure 1]. Intraoral examination revealed an early mixed dentition stage, with erupted upper and lower permanent central incisors and first molars. All maxillary teeth from the primary right canine (53) to the left first molar (64) were in crossbite with the mandibular primary first molar on the right side (84) to the first molar on the left side (74), except for the maxillary right primary lateral incisor (52) which was partially locked [Figure 2]. The molar relation on both sides was developing class III malocclusion, with the mandibular molar being 3 mm ahead of the buccal cusp tip of the maxillary molar. There was no family history of class III malocclusion. On assessment of the CR-CO discrepancy and guidance of the mandible on closure, a functional shift of the mandible was seen. An occlusal prematurity in relation to erupting 11 appeared to be responsible for the present functional shift [Figure 3]. The maxillary growth seemed to be restricted due to the postural shift of the mandible in a class III position. A lateral cephalogram revealed that the point A was in the range of normal, whereas the point B was slightly greater than the normal [Table 1]. Based on the above findings, a diagnosis of pseudo class III malocclusion was made.
The treatment was aimed at eliminating the anterior interlock. Since there was no maxillary growth restriction [Table 1] and the mandible was observed to be at fault on closure, a decision to treat the patient with a reverse twin block appliance was made; it was expected to position the mandible backwards and promote maxillary growth. The method comprised the usual wax bite registration in a position of maximum retrusion of the mandible. Following this, upper and lower bite blocks were fabricated in heat cured PMMA, with clasps on the maxillary and mandibular permanent first molars. The bite blocks were made to cover the upper primary first and second molars and lower permanent first molars with a reverse direction of the inclined planes [Figure 3a]. A lower anterior passive labial bow was also incorporated for the purpose of retention. The patient was instructed to wear the appliance for as long as possible and also during mealtimes. The patient compliance during eating was poor in the first 2 months of treatment. It, however, improved after motivation and counseling of both the child and the parents. Improvement in the profile on wearing the appliance also acted as a positive motivation factor. The appliance was activated every 3 weeks by addition of acrylic resin on the inclines of the bite blocks. The patient developed a habitual closure of the mandible in a backward position and correction of the anterior crossbite within 2 months of wearing the appliance. The patient was made to continue the appliance for another 6 months for the purpose of retention. At the end of 10 months, a significant improvement in the patient's profile was noted [Figure 4]. Post-treatment cephalometric readings showed an increase in SNA by 2° i.e. from 82°-84° of 84° and no change in the SNB angle [Table 1]. The ANB changed from −2° preoperatively to 0° postoperatively. Though the ANB was still zero, there was a marked improvement in the profile which was expected to improve further and to possibly affect the ANB angle. The effects observed were attributed to the unrestricted growth of the maxilla following correction of interlocking and also the guidance of the mandible in a normal backward position. The pretreatment and post-treatment FMA readings were 26° and 27°, respectively [Table 1]. The intraoral examination after a 2-year follow-up revealed a normal overjet and overbite relation [Figure 5].
A 7-year-old boy presented with the chief complaint of abnormally placed upper and lower teeth and also decayed teeth. On extraoral examination a concave profile was seen, with an everted lower lip; maxillary deficiency was very evident [Figure 6]. Intraoral examination revealed mixed dentition stage, with erupted permanent maxillary central incisors (11,21) and first molars, and erupting right permanent lateral incisor, lower central (12), and left first premolar (24). The maxillary primary first molars (54,64) had been lost due to caries and the right second molar (55) was cariously exposed. In the lower arch, the permanent incisors and first molars were erupted. Mandibular left primary molars (74,75) were badly broken down, requiring extractions, and the right side molars (84,85) needed restorations. Assessment of occlusion revealed that the child had a developing class III molar relation along with an anterior crossbite [Figure 7]. He was, however, able to slide the mandible backward to bring it to an anterior edge-to-edge bite. No premature incisal contacts were observed at this stage of eruption of teeth. Cephalometric analysis revealed a decreased SNA (75°) and a normal SNB, though it was on the lower side (78°) [Table 1]. There was no familial tendency of true class III malocclusion and the profiles of both parents were normal. Since the point A was deficient and the point B was not increased, a decision to correct the anterior interlock by bringing the maxilla forward using face mask therapy was made. Prior to the orthodontic intervention, all the carious teeth were restored or extracted and the extaction spaces in the lower arch were maintained with a lingual arch space maintainer. An intraoral splint was fabricated on the prepared casts. The face mask (Leone) was adjusted 24 h after cementing the splint and the patient was instructed to wear it for 14-16 h/day and change the elastics daily [Figure 8]. Adequate maxillary protraction was achieved within 5 months' time [Figure 9]. Since a functional mandibular shift was still present, for the purpose of retention a reverse twin block appliance was fabricated and given to the patient. The bite blocks were trimmed at regular intervals to permit settling of the occlusion and were discontinued after 6 months when this was achieved. The postoperative cephalometric readings [Table 1] after 18 months' follow-up showed an increase by 4° in the SNA value of 79° and an increase of 2° in the SNB value of 80°. Though the ANB remained −1°, from −4° preoperatively, the improvement in the patient's profile was marked [Figure 10]. The FMA increased by 2°, from 20° preoperatively to 22° postoperatively.
An 11-year-old boy reported with the chief complaint of backwardly placed upper front teeth and forwardly closing lower jaw. Extraoral examination revealed a concave profile with a prominent chin [Figure 11]. Intraorally, class I molar relationship on the right side and a mild class III relationship on the left side, along with a forward mandibular functional shift on closure, were present [Figure 12] and [Figure 13]. The patient was in the mixed dentition stage with erupted permanent maxillary and mandibular incisors and first molars; the primary molars and canines were still present. No tooth was carious and the oral hygeine was satisfactory. Cephalometric analysis revealed a normal SNA value of 83° and an increased SNB value of 85°, indicating unrestricted mandibular growth [Table 1]. The ANB was −2°. The soft tissue clinical assessment was, however, indicative of maxillary retrusion. The parents and siblings did not show any signs of class III malocclusion. Since the maxillary skelatal base was not at fault and fullness of the soft tissue in the anterior segment was obviously deficient, a decision to fabricate an anterior expansion appliance, along with posterior bite plates to correct the dentoalveolar relation by bringing the maxillary incisors out of crossbite, was made. The expansion appliance was activated by the patient every third day. Correction of overjet was seen within 3 months of the appliance delivery, following which the bite plates were sequentially trimmed to settle the occlusion [Figure 14]. In this case, initially, despite the SNA being 83°, the soft tissue depicted a maxillary retrusion and hence in the final correction of the malocclusion as well, the cephalometric parameters give only an indication of the maxillo-mandibular position to the cranial base but may not necessarily finally influence the profile, the improvement in which was only slight [Figure 15]. The patient was kept under follow-up to observe the effects of unrestricted growth after removal of the interlock.
| Discussion|| |
Various types of skeletal patterns have been shown to exist with class III malocclusions.  These may be a result of (i) genetic predisposition or (ii) occlusal prematurities leading to abnormal closure patterns that remained undiagnosed and worsened with time. Angle  suggested that the latter begin at the time of eruption of the permanent first molar or even earlier and are associated with enlarged tonsils and the habit of protruding the mandible. More likely, it develops with the eruption of the permanent incisors in a malposed position. Because of a premature contact, the child closes the mouth in the most convenient position to establish occlusion, which leads to protrusion of the mandible; it may or may not be associated with enlarged tonsils. This condition if untreated early, at the time of its development in the growth period, often results in a permanent alteration in the pattern of closure, aberrant growth, and subsequent facial deformity. Treatment in all developing class III cases should be undertaken as soon as the abnormality is diagnosed to prevent it from becoming permanent and resulting in a full-blown class III malocclusion.  This is especially true in girls, as a protruded mandible renders a very rigid, unpleasant facial appearance in females.
The various treatment options available for the management of developing class III malocclusion are: (i) functional appliances such as reverse twin block, Frankel appliance, and the removable mandibular retractor; (ii) orthopedic appliances like chin cap and face mask; and (iii) orthodontic appliances viz. removable maxillary expansion plate or fixed orthodontic appliance with expanded upper arch wire. Basically, for the early management of the cases of pseudo class III malocclusion, the clinician faces the challenge of (i) redirecting the mandibular closure, (ii) removing the occlusal prematurity, and (iii) correcting the maxillo-mandibular relationship. To achieve this, out of the above mentioned options, a treatment plan may be chosen depending on the extent of maxillary growth restriction, mandibular plane angle, the soft tissue profile, and the age of the patient.
When the condition is such that the forward shift of the mandible has resulted in an increased SNB value and has caused very little maxillary restriction, an appliance which positions the mandible backwards, such as a reverse twin block, is ideal. This appliance, on being worn, causes an immediate improvement in the patient's profile and also habitually programs the mandible into a new neuromuscular position (NMP). In the first case report of the series, the 8-year-old girl with the above features was successfully treated using this appliance. The overall treatment time was approximately 10 months, inclusive of the retention period. The mandibular plane angle increased from 26° to 27° postoperatively [Table 1]. The patient showed a skeletal change, with a 2° increase in the SNA angle, indicating normal growth of the maxilla. The reverse twin block has been gaining importance ever since its inception by Clark.  Kidner et al.  in their evaluation of the reverse twin block appliance on 14 subjects less than 12 years of age found that the changes were mainly dentoalveolar and the skeletal changes limited to slight downward and backward rotation of the mandible. The average treatment time was only 6.6 months.
The ideal cases for a reverse-pull headgear are the ones that show skeletal maxillary retrusion, preferably with a low mandibular plane angle. The face mask therapy can be started as soon as the patient can handle the appliance and is willing to wear the appliance.  The face mask acts by causing forward movement of the maxilla and restricting the mandibular growth; there is also associated downward and backward rotation of the mandible.  Children with moderate to severe maxillary retrusion and steep mandibular plane angles may also be treated with this method to correct the maxillary deficiency, which is essential in these cases; however, this is at the cost of making the mandibular plane still steeper.  The most undesirable effect is the upward movement of the maxilla. This can be controlled by applying forces in a direction 30° downward to the occlusal plane, the point and direction of force application being very important. The face mask is an ideal option for the treatment of cases of developing class III malocclusion when the condition has resulted in severe maxillary growth restriction [Table 1] and [Figure 6], as in the patient in case report 2 of the series. In this case, the face mask was effective in correcting the functional mandibular shift with severe maxillary restriction. The mandibular plane angle in this case increased from 20° to 22° postoperatively.
In developing class III malocclusion in which the maxillary and mandibular skeletal bases are normal and the anterior shift of the mandible results in a dentoalveolar crossbite, the treatment of choice is an anterior expansion appliance to correct the anterior maxillary interlock and allow for normal maxillo-mandibular growth. One such appliance was used in the third case report in this series and was found to be effective. In this patient, however, after treatment the mandibular incisors showed retroinclination, indicative of a developing true class III pattern. Even though there is no family history of malocclusion in this case, the child needs to be kept under observation till the time he passes the third growth spurt at 18 years of age.
The other appliances used for the management of developing class III problems, but not used in the present series, are (i) the chin cap, (ii) the Frankel appliance, and (iii) the reverse mandibular retractor. The chin cap is one of the earliest used appliances to restrict the overgrowing mandible. It is indicated primarily in the deciduous and early mixed dentition phase and has been shown to have an orthopedic effect on the mandible by controlling the mandibular growth at the chin.  It causes a downward and backward rotation of the mandible, thus increasing the mandibular plane angle; it is not indicated in steep mandibular plane angle cases. Being an extraoral appliance, compliance of the child is essential. With the use of the chin cap, the overall results are unpredictable and generally depend on the amount of force applied and the duration of daily wear.  Like twin block, the Frankel appliance  is a commonly used functional appliance for the treatment of pseudo class III malocclusion. The clinical efficacy of this appliance has been widely studied since its introduction. Ulgen et al.  studied the effect of the Frankel functional regulator on 40 functional class III malocclusion subjects with the mean age of 9.5 years and found a significant increase in the ANB angle as a result of decrease in the SNB angle due to a downward and backward rotation of the mandible. The effect of FR-3 treatment was less marked on the SNA angle, which did not show a significant difference compared to the matched control group. Robertson et al.  observed only dentoalveolar changes and no skeletal changes in children with mean age 9.4 years treated with the FR-3 appliance. This appliance, which requires technical skill, precision, and time for fabrication, also results in an increase in the mandibular plane angle. Another, more recent, intraoral appliance that has been used for restricting mandibular growth and has shown promising results is the removable mandibular retractor,  which is a maxillary resin plate with labial arch wire extending to the labial surfaces of the mandibular incisors. In our opinion, this appliance mainly acts by providing proprioceptive stimuli to restrict the forward movement of mandible. Baccenti et al.  used this appliance, along with an expansion screw, on two groups of children with class III malocclusions: during deciduous dentition in one group and during mixed dentition in the second group. They found positive skeletal changes in children treated during deciduous dentition and dentoalveolar protrusions in those treated during mixed dentitions. Since this appliance does not have a vertical vector of force it may also be used in children with a steep mandibular plane angle.
| Conclusion|| |
The basic aim of all treatment in a developing class III malocclusion, with or without positional malrelations, is to enable the child to close the mouth in normal centric relation by removing the anterior interlock, thus permitting normal growth. The earlier such a case presents to the clinician and is diagnosed, the simpler and faster is the treatment. The selection of an appropriate treatment modality mainly depends on the extent of maxillary growth restriction; in severe cases, the treatment revolves around face mask and in less severe cases, twin block. For the selection of a case for a functional appliance, two things are to be kept in mind: (i) there should be minimal maxillary skeletal deficiency and (ii) the mandibular plane angle should not be very steep. The clinical assessment of soft tissue coverage and overall esthetics also plays an important role in the selection of a treatment modality, as sometimes a slight increase in the vertical height of the face in steep-angle cases may not affect the overall esthetics and may even add to it, depending on the facial profile. Among the functional appliances all except the removable mandibular retractor will lead to increase in the mandibular plane angle. No appliance, however, is truly functional as some mechanical component may have to be incorporated into it with time and need. The face mask also leads to an increase the mandibular plane angle [Table 1]. The expansion plate with posterior bite plate, as a means to correct the anterior interlock, will also lead to an increase of the vertical height of the face. In cases where the skeletal maxillo-mandibular relation is normal, the removable anterior expansion plate or a fixed appliance with an expanded arch wire is more suitable for dentoalveolar corrections.
The key to the successful management of such cases, therefore, is to remove the anterior interlock as early as possible so as to allow for the normal unrestricted growth of the maxilla and also to guide the mandible to a normal retrusive position. The earlier the treatment is carried out, the faster and more stable are the results.
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[Figure 1], [Figure 2], [Figure 3], [Figure 3a], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15]
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